Recently, printing devices using inkjet recording method, such as inkjet printers and inkjet plotters, have been widely used in not only printers for general consumers but also industrial purposes, such as manufacturing of color filters for forming electronic circuits and for liquid crystal displays, and manufacturing of organic EL displays.
In the inkjet method printing device, a liquid discharge head for discharging liquid is mounted as a printing head. For this type of print head, thermal method and piezoelectric method are generally known. That is, in the thermal method, a heater as a pressing means is installed in an ink passage filled with ink, and the ink is heated and boiled by the heater. The ink is pressed by air bubbles occurred in the ink passage, and is then discharged as liquid drops through ink discharge holes. In the piezoelectric method, a part of the ink passage filled with ink is bendingly displaced by a displacement element. The ink in the ink passage is mechanically pressed and is discharged as liquid drops through the ink discharge holes.
The liquid discharge head can employ either serial method or line method. That is, with the serial method, recording is carried out while the liquid discharge head is moved in a direction orthogonal to a transport direction of a recording medium. With the line method, recording is carried out on a recording medium transported in a sub scanning direction in a state where a liquid discharge head being longer in a main scanning direction than a recording medium is fixed, or in a state where a plurality of liquid discharge heads are arranged and fixed so that a recording range becomes larger than a recording medium. The line method has an advantage of permitting high speed recording because unlike the serial method, there is no need to move the liquid discharge head.
Even the liquid discharge head of either the serial method or the line method is required to increase the density of the liquid discharge holes for discharging the liquid drops which are formed in the liquid discharge head, in order to print the liquid drops with high density.
For example, there is known a liquid discharge head that is configured by laminating a manifold; a plate-shaped passage member having individual passages connecting between the manifold and the liquid discharge hole through an aperture, a liquid pressurizing chamber, and a communication passage which are sequentially arranged from the manifold side and in order of their listing; and an actuator unit having a plurality of displacement elements provided to respectively cover the liquid pressurizing chambers (refer to, for example, patent document 1). In this liquid discharge head, by displacing the displacement elements 550 of the actuator unit provided to cover the liquid pressurizing chambers, liquid drops are discharged from individual liquid discharge holes respectively connected to the liquid discharge chambers, thus permitting printing at a resolution of 600 dpi in the main scanning direction. In the liquid discharge head, in a plane view thereof, the rhombic liquid pressurizing chambers are arranged in a matrix shape. Individual electrodes for driving the displacement elements are respectively made up of an individual electrode body overlapped with the liquid pressurizing chamber, and a connection electrode led out from the individual electrode body to outside the liquid pressurizing chamber.
The passage member is one in which a plurality of metal plates are laminated one upon another. A piezoelectric actuator is one in which a piezoelectric ceramic layer, a common electrode, a piezoelectric ceramic layer, and an individual electrode are laminated one upon another from the passage member side and in order of their listing.